$ C = \left[\begin{array}{rrr}-1 & 4 & -2 \\ 0 & -1 & 1 \\ -2 & 4 & 2\end{array}\right]$ $ B = \left[\begin{array}{rrr}4 & 3 & 2 \\ 4 & -2 & 4 \\ 2 & -1 & -1\end{array}\right]$ Is $ C+ B$ defined?
Explanation: In order for addition of two matrices to be defined, the matrices must have the same dimensions. If $ C$ is of dimension $( m \times  n)$ and $ B$ is of dimension $( p \times  q)$ , then for their sum to be defined: 1. $ m$ (number of rows in $ C$ ) must equal $ p$ (number of rows in $ B$ ) and 2. $ n$ (number of columns in $ C$ ) must equal $ q$ (number of columns in $ B$ Do $ C$ and $ B$ have the same number of rows? Yes Yes No Yes Do $ C$ and $ B$ have the same number of columns? Yes Yes No Yes Since $ C$ has the same dimensions $(3\times3)$ as $ B$ $(3\times3)$, $ C+ B$ is defined.